Food for the brain

Minding what you eat may help preserve mental capacity as you age

March 03, 2004|By Betsy Hornick, Special to the Tribune. Betsy Hornick is a dietitian and freelance nutrition writer in Poplar Grove, Ill.

What if mental decline did not have to be a natural consequence of aging? What if part of the secret to staying sharp lies in the foods we eat?

The notion that memory loss and changes in brain function are a natural part of the aging process is being challenged. Emerging evidence suggests that getting enough of certain nutrients--namely iron, zinc and B vitamins--may help stave off cognitive decline seen with aging, possibly even Alzheimer's and dementia.

Cognitive function, which encompasses many aspects of brain power including memory, reasoning, perception, concentration and ability to learn, is a precious possession, especially as we age. Preserving your brainpower may be easier than you think.

"We're learning that if you feed your brain the right nutrients, it will work harder for you throughout life," said Dayle Hayes, dietitian, author and nutrition therapist in Billings, Mont.

It is well-known that iron deficiency impairs brain development and learning in children. "The adult brain may also be affected by iron deficiency," said Mary Kretsch, research physiologist with USDA's Agricultural Research Service at the Western Human Nutrition Research Center in Davis, Calif.

Recent studies conducted by Kretsch and her colleagues found a decline in concentration and short-term memory associated with low iron intakes in women who were dieting. In men, as iron and zinc levels in the body declined, notable decreases in attention span were measured. Cognition studies like these measure brain function, such as memory, perception, concentration and spatial ability, using special standardized tests.

A surprising and significant finding also became evident: The ability to concentrate declines prior to the onset of iron and zinc deficiency.

"Normally, a deficiency develops and then functional changes occur," Kretsch says. "But with iron and zinc, levels in the body are in ranges of what's considered normal when declines in cognition begin to occur. This is a real concern, especially for people wanting optimal mental productivity, since the effects of iron and zinc deficiency occur earlier than we would have predicted."

B vitamin benefits

There is growing evidence that getting enough B vitamins can prevent, slow or reverse deterioration in memory and other mental capacities. B vitamins--particularly folic acid (or folate), vitamin B6, and vitamin B12--play a role in the production of important brain chemicals required for cognition and other brain functions.

The Normative Aging study--ongoing research of aging in men by the Massachusetts Veterans Epidemiology Research and Information Center--found that low blood levels of vitamin B12 and folic acid were associated with changes in spatial ability. Higher blood levels of vitamin B6 were linked to better performance on memory tests.

Researchers also are examining the effects of B vitamins from another angle. It seems that individuals with Alzheimer's and dementia have higher levels of an amino acid called homocysteine in their blood. B vitamins help to break down homocysteine in the body. Increased homocysteine levels have also been linked to a greater risk for heart disease and stroke.

"B vitamins have a protective effect by keeping homocysteine levels from rising," said Katherine Tucker, associate professor at the Tufts University School of Nutrition Science and Policy.

"There is an amazing correlation," Tucker said. "When B vitamin intake is low, homocysteine levels rise, and we find a decline in brain function." Under these conditions, Tucker and colleagues have measured impairments in memory, language, attention, perception and spatial ability. Over a lifetime, Tucker and other researchers speculate that this may influence risk for developing Alzheimer's and other types of dementia in later years.

Food for thought

Experts agree that in most instances wise food choices can prevent nutrient deficiencies. The one exception to this is vitamin B12 for older adults.

"Vitamin B12 deficiency is a common problem among the elderly," Tucker said. "Even if older adults manage to consume enough B12, which is found bound to the protein in meat and dairy products, they often suffer from an age-related decrease in stomach acid that prevents them fully absorbing vitamin B12." This is why adults over age 50 are advised to take a vitamin B12 supplement or get this vitamin from fortified foods, such as breakfast cereals.

Supplements of iron and zinc are an option too. But Kretsch cautioned that relying on supplements can be a problem if you consume too much of either nutrient. "The wrong ratio of iron and zinc can cause an imbalance of either nutrient," which can lead to other problems.

Iron and zinc are available in, and best absorbed from, meat, poultry and seafood. Fortified breakfast cereals, whole grains and dried beans are also good sources.

"Hands down, the best source of both iron and zinc is lean beef," Hayes said. The iron and zinc in plant foods is not as easily absorbed.